This invention relates to a method of processing waste on ships and the like, the waste being partly in the form of solid matter and partly in the form of black water coming from reduced-flush toilets and conveyed to and collected in a tank. The invention also relates to an arrangement for carrying out the method.
In the past, all waste from ships was, as a rule, discharged overboard without purification. However, due to the increasing emphasis on environmental protection, this practice can no longer be accepted, and new systems have been introduced with the object of neutralizing and storing the waste on the ship until it arrives in port, whence the waste is transferred ashore. Thus, for example, vacuum systems for sewage have been used in which the toilets are connected to a vacuum tank, so that the waste is conducted to a tank by vacuum force. This system has proved very satisfactory for handling black water, since only a small quantity of flush and transport liquid is required which can thus be collected in comparatively small space-saving tanks. This system has the additional advantage that it is not necessary to convey the water by gravity, so that the conduits can be placed at almost any desired location on the ship.
However, there are also other types of waste on ships and such refuse has been found to be difficult to take care of. Therefore, there is an urgent need for a more complete system which handles all waste on ships and if possible transforms it into a product which is easy to handle, odor-free and, if desired, sterile.
Briefly stated, this objective is achieved by the method according to the invention wherein the solid waste, after or during disintegration, is passed through a treatment zone is which it is caused to fall by gravity in a flow of hot air. The black water being conducted to the treatment zone and mixed with the solid, disintegrated waste, which thus serves as a carrier and an exposure surface for the black water in the hot-air flow. The hot-air flow evaporates all the liquid in the waste in the final part of the treatment zone, so that a dry product is obtained.
A preferred apparatus for performing the method includes a generally horizontal drum having an intake for heated air at one end and an outlet for this air at its opposite end. An inlet for solid waste, an inlet for liquid waste in the form of black water, and an outlet for dried waste are provided in the drum. A rotatable agitator is disposed in the drum to lift the waste from the bottom cause it to fall by gravity in the air flow.
In addition to the black water, waste on ships usually comprises what is generally called grey water, i.e. water from bath tubs, kitchen and lavatories. Further, waste is in the form of kitchen refuse, packings, such as paper, plastics products, can, etc., as well as oil, cargo spillings, paint, wood, saw dust, garbage, etc. All this refuse can be processed and transformed into a dry product according to the system of the invention.
The system does not take care of the whole quantity of liquid contained in the grey water, since its contents of polluting substances in grey water is small relative to its total quantity and thus can be discharged overboard without too much harm. The grey water can, however, be processed by a conventional purification method for recovering the solid particles, which are then introduced into the process with the solid waste.
The invention is particularly adapted to operate with so-called reduced-flush toilets and will not function with conventional toilets, in which the liquid quantity is too large to be handled in a practical manner .